1. Field of the Invention
The present invention relates to a cigarette lighter adapter assembly used, for instance, in conjunction with a cellular phone and, more particularly, to a cigarette lighter adapter having a plunger retention mechanism for insuring that the contact plunger of the adapter is not lost while replacing or checking a fuse in the adapter.
2. Description of the Related Art
Cigarette lighter adapter assemblies used, for example, in conjunction with cellular telephones (hereinafter "cell phone") to facilitate use of the cell phone while driving an automobile have proliferated in recent years due to the increasing popularity of cell phones in our car-oriented culture. Such cigarette lighter adapter assemblies provide a power source for cell phones by interconnecting the phone to a car battery through the cigarette lighter.
A conventional cigarette lighter adapter assembly is characterized by three main components, as shown in FIG. 1. Specifically, a cell phone plug 10 and a cigarette lighter adapter 20 are interconnected by means of a power cord 30, preferably a flexible, extendable, coiled power cord. The cell phone plug 10 is adapted to be removably-connected to an input terminal on a conventional cell phone (not shown). Similarly, the cigarette lighter adapter 20 is designed to be removably-connected to a conventional cigarette lighter (not shown).
In operation, power from the car battery is provided to a cell phone through, respectively, the cigarette lighter adapter, power cord and cell phone plug of the assembly. Diverse known preferred features are provided on different adapters. For instance, it is known to provide a cigarette lighter adapter assembly which can charge the cell phone battery, as well as override the phone's battery when the phone is connected to a car battery to amplify or preserve the charge on the cell phone battery.
A typical 12 or 24 V DC cigarette lighter adapter 20 is illustrated in cross-section in FIG. 2. As shown therein, a housing generally indicated at 21 includes main body 22 and apertured cap 23. Cap 23 has a threaded circumferential end 23a adapted to be threaded onto a threaded end 22a of main body 22. Those of ordinary skill will appreciate that variations on the illustrated assembly are known including, for example, that cap 23 may be externally threaded to mate with female threading on the main body 22. Spring-biased fuse 24, e.g., a 2 A fuse, is removably-situated in the interior of main body 22. Retractable metal plunger 25 having contact element 25a and integrally-formed base element 25b are removably-situated in cap 23 such that contact element 25a extends through aperture 26 in cap 23. When the adapter is inserted into a car cigarette lighter, contact element 25a provides a connection to the car battery power source, metal plunger 25 retracts in direction A, and base element 25b contacts and depresses fuse 24, thus interconnecting the car battery and a cell phone (not shown) connected to cell phone plug 30 and providing DC power to the cell phone (e.g., 8.2 V; 850 mA).
Between uses, fuse 24 can be checked or replaced by removing cap 23 and extracting fuse 24 by hand. However, this procedure often results in the loss or misplacement of plunger 25, which is loosely and removably-situated in cap 23, thus rendering the adapter unusable. The inconvenience resulting from such a design is manifest and can easily occur at inopportune times, for example, while driving the car.
Accordingly, the need currently exists for a cigarette lighter adapter assembly and adapter which not only achieves its intended function of allowing use of a cell phone from a car, but also minimizes the potential for loss of critical parts and the predictable attendant disadvantages.